For example, JP-A-2001-244394 discloses that thermal conductive grease (hereinafter referred to as heat releasing gel) is interposed between a semiconductor package and a heatsink so as to release heat generated from the semiconductor package.
Recently, since a vehicle-mounted motor and an electronic control unit (hereinafter referred to as ECU) for driving the motor are often used, volume occupied by the motor and the ECU tends to be increased. On the other hand, in order to extend vehicle interior space, the space for arranging the motor and the ECU is decreased. Therefore, miniaturization of the motor or the ECU is desired.
For example, since an electronic control unit used for an electronic power steering system (hereinafter referred to as EPS) that assists steering by a driver needs to be energized by large current to drive a motor, and thereby its heating value becomes large. Therefore, it is necessary to improve heat releasing performance while miniaturizing the electronic control unit.
However, as disclosed in JP-A-2001-244394, in the case where the heat releasing gel is used for the ECU of a vehicle to improve the heat releasing performance, there was a problem that the heat releasing gel moves due to the influence of vibration or the like.